Inflatable inner molds have been used for making containers. Generally plastic or rubber bags have been inflated to provide the inner mold during the molding process and then deflated and removed after the process has been completed.
When the large housings or containers are to be molded, relatively large inflatable members are required. Single piece inflatable members generally involve seaming a number of small pieces, made of nylon or polyurethane, for example, to provide the large inflatable member. A problem using such seams is that they provide weak areas in the inflatable members which tend to result in leakages or breakage if the inner mold is not precisely dimensioned and located when pressures are applied to produce the inner mold. Heretofore, certain materials used for inflatable members, such as silicon or rubber, which can be seamed without weak joints, have been subject to attack by the resin materials used in the molding process.
The inner mold of the present invention is directed towards producing a seamless, one piece non-metallic shelter for applications, such as military use. Military shelters have generally involved the use of aluminum faced panels. Generally, these shelters do not have the high performance relating to resisting environmental degradation.
Some patents related to inflatable inner molds and features of the present invention include U.S. Pat. Nos. 2,644,198; 1,381,179; 3,937,781; 4,183,778 and 4,118,451.